Ion implantation is a conventional technique for introducing dopants into semiconductor materials. A desired dopant may be ionized to form a plasma in an ion source. The ions are accelerated from the source to form an ion beam of selected energy which may be directed at the surface of a semiconductor wafer. The ions in the beam penetrate into the semiconductor wafer to form an implanted region.
In some processes, it is desirable to implant helium in a semiconductor wafer. One conventional technique involves introducing pure helium gas into an arc chamber of an ion source. Current is passed through a filament located in the arc chamber, and a voltage is applied to generate a plasma that includes helium ions within the chamber. However, because helium has a high ionization potential and a small molecular size, the generation of helium ions is typically inefficient. Thus, helium ion beams that are formed utilizing such techniques typically have relatively low beam currents which may be unsuitable for use in some implantation processes.